linux-kernel - Re: [PATCH RFC 1/7] x86/virt/tdx: Add SEAMCALL wrapper to enter/exit TDX guest

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Message-ID: <edcc2f0d-8e02-4ec9-8ca3-c2452fcdf8ff@intel.com>
Date: Mon, 25 Nov 2024 15:43:22 +0200
From: Adrian Hunter <adrian.hunter@...el.com>
To: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
 "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
 "pbonzini@...hat.com" <pbonzini@...hat.com>,
 "Hansen, Dave" <dave.hansen@...el.com>, "seanjc@...gle.com"
 <seanjc@...gle.com>,
 "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>
Cc: "Gao, Chao" <chao.gao@...el.com>, "Yang, Weijiang"
 <weijiang.yang@...el.com>, "x86@...nel.org" <x86@...nel.org>,
 "Huang, Kai" <kai.huang@...el.com>,
 "binbin.wu@...ux.intel.com" <binbin.wu@...ux.intel.com>,
 "Li, Xiaoyao" <xiaoyao.li@...el.com>,
 "Chatre, Reinette" <reinette.chatre@...el.com>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "tony.lindgren@...ux.intel.com" <tony.lindgren@...ux.intel.com>,
 "dmatlack@...gle.com" <dmatlack@...gle.com>,
 "Zhao, Yan Y" <yan.y.zhao@...el.com>,
 "Yamahata, Isaku" <isaku.yamahata@...el.com>,
 "nik.borisov@...e.com" <nik.borisov@...e.com>
Subject: Re: [PATCH RFC 1/7] x86/virt/tdx: Add SEAMCALL wrapper to enter/exit
 TDX guest

On 22/11/24 19:29, Edgecombe, Rick P wrote:
> On Fri, 2024-11-22 at 08:26 -0800, Dave Hansen wrote:
>> On 11/21/24 12:14, Adrian Hunter wrote:
>>> +u64 tdh_vp_enter(u64 tdvpr, struct tdx_module_args *args)
>>> +{
>>> +   args->rcx = tdvpr;
>>> +
>>> +   return __seamcall_saved_ret(TDH_VP_ENTER, args);
>>> +}
>>> +EXPORT_SYMBOL_GPL(tdh_vp_enter);
>>
>> I made a similar comment on another series, but it stands here too: the
>> typing of this wrappers really needs a closer look. Passing u64's around
>> everywhere means zero type safety.
>>
>> Type safety is the reason that we have types like pte_t and pgprot_t in
>> mm code even though they're really just longs (most of the time).
>>
>> I'd suggest keeping the tdx_td_page type as long as possible, probably
>> until (for example) the ->rcx assignment, like this:
>>
>>       args->rcx = td_page.pa;
> 
> Any thoughts on the approach here to the type questions?
> 
> https://lore.kernel.org/kvm/20241115202028.1585487-1-rick.p.edgecombe@intel.com/

For tdh_vp_enter() we will just use the same approach for
tdvpr, whatever that ends up being.